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Co-founder and CEO of Neural DSP Doug Castro reveals the dark art of guitar amp modelling

Neural DSP Quad Cortex
(Image credit: Neural DSP)

Great guitars are a multisensory experience. 

Okay, smell might not be top of the list (and hopefully taste (opens in new tab) doesn’t factor into the equation at all!) 

However, if the instrument manages to tick all the boxes in terms of look, sound and feel then it’s a winner.

Similarly, when it comes to guitar amps, we can easily trust our eyes and ears. 

But the ‘feel’ of an amp? That’s when things get a little more complicated.

So complicated, in fact, that Doug Castro – co-founder and CEO of Neural DSP (opens in new tab) – believes this to be the single most difficult aspect of guitar amp modelling.

“The hardest part to model in an amplifier is actually the dynamic response – how it feels on the fingers,” Castro tells MusicRadar in a new interview.

“I think there are many emulations that [sound] super-close to the amp if you re-amp through them. But when you play through them they feel a bit odd.”

Needless to say, we would never recommend literally touching anything inside a guitar amp. Rather, the sense of 'feel' is determined by an interactive set of components that uniquely influences the electric guitar signal and, consequently, the player’s response.

“What is responsible for that is the energy transfer,” adds Castro. “From the amp’s power supply, through the power tubes, through the output transformer, out into the reactive load, and the speaker.

“All of these things have these super-weird effects on the guitar signal that are noticeable and perceivable.

“I don’t think this is very well understood to this day, and I don’t think we will ever have good science done on this because it is just not profitable for anyone to research the [idiosyncrasies of an] output transformer.”

So, how does Neural DSP navigate this dark art so successfully with the Quad Cortex (opens in new tab)

According to Castro, their approach to amp modelling means they don’t need to fully understand the minutiae of circuitry in order to recreate the same kind of feel.

“Based on what we measure the model writes itself,” he reveals. “If you can hear it and feel it our model will take that into account.

“I think the touch response is one of the things that we are known for – one of the things I feel is really, really close to the real thing.

“If I open my SVT or a Fender Bassman, they feel different, just like the amps do.”

For more information on the Quad Cortex visit Neural DSP (opens in new tab).

Rod Brakes
Rod Brakes

Rod Brakes is a music journalist with an expertise in guitars. Having spent many years at the coalface as a guitar dealer and tech, Rod's more recent work as a writer covering artists, industry pros and gear includes contributions for leading publications and websites such as Guitarist, Total Guitar, Guitar World (opens in new tab)Guitar Player (opens in new tab) and MusicRadar (opens in new tab) in addition to specialist music books, blogs and social media. He is also a lifelong musician.